Telephones are used by many people around the world to communicate with each other. In order to satisfy customer needs and to provide additional sources of income, telephone companies often provide additional telephone services, e.g., call screening, call forwarding, voice dialing, etc., beyond the basic telephone service to which users have grown accustomed.
These additional or enhanced services can be implemented in a Signal Switching Point (SSP), e.g., a telephone switch, and/or through the use of Advanced Intelligent Network (AIN) functionality. Switched based services tend to be more limited than AIN based services since they are limited by the functionality available in the telephone switch. AIN based services tend to be more robust than switched based services since they are implemented using the considerably more advanced control capability of a service control point (SCP). SCPs operate under software control, e.g., at the direction of processing instructions included in a Call Processing Record (CPR) associated with an individual service subscriber.
Telephone switches normally include an Automatic Route Selection (ARS) table or tables that are used to determine, for switch based ARS subscribers, which telephone trunk should be used to route a call originating from the subscriber. An ARS table normally includes one or more sets of numbers corresponding to the initial digits of a telephone number, e.g., directory number (DN), and a route index for each set of numbers. The route index identifies the trunk over which calls matching the corresponding set of numbers, should be routed for the customer to whom the particular ARS table corresponds. Different trunks used to connect SSPs often correspond to different carriers. Thus, ARS allows a customer to automatically route calls over preferred, e.g., least cost, carriers.
In switch based ARS, when the ARS customer makes a call, the SSP normally accesses the ARS table corresponding to the customer placing the call and determines which route index should be used for call routing to the particular called party directory number (DN) to which the call is directed. The SSP then attempts to route the call via the trunk specified by the route index obtained from the customer's switch based ARS table.
In an AIN system, triggers are set at signal switching points (SSPs), e.g., telephone switches, to detect one of a number of call processing events. In response to the activation of an AIN trigger, an SSP suspends processing of the call that activated the trigger, compiles a message and forwards that message via a common channel interoffice signaling (CCIS) link to a Service Control Point (SCP). Some SCPs are implemented as integrated service control points (ISCP) which include functionality for provisioning AIN services for customers. AIN triggers can occur at any one of several points during the processing of a call.
Once sufficient information about the call has reached the SCP, e.g., via the message from the SSP, the SCP accesses stored call processing information, e.g., a call processing record (CPRs) and generates a message which is returned to the SSP where the trigger was activated. The SSP then resumes call processing following any instructions received from the SCP.
Unfortunately, most telephone switches resume call processing following an AIN trigger at a point which results in the switch's ARS table functionality being bypassed. This can have the unfortunate effect of causing a call which is subjected to AIN processing to be routed by a carrier other than the lowest cost service provider.
An ever increasing number of new telephone services are being implemented as AIN based services rather than switch based services. This is due, in part, to the greater control/processing that the SCP can provide as compared to individual switches. If AIN services are to gain widespread acceptance and use by ARS services subscribers, there needs to be a way to provide ARS functionality in conjunction with AIN services. Absent the ability to provide ARS service in conjunction with AIN services, the potential additional cost associated with failing to use a customer's least cost routing service provider will discourage the use of AIN services.
One telephone switch vendor, Nortel Networks, has added to its telephone switches, e.g., DMS-100 switches, a capability where, in response to receiving a route index having a specific value from an SCP, telephone switch will process the call using the switch's ARS table. In this manner AIN service subscriber's who are serviced by the DMS-100 switch, in some cases, can receive the benefit of a switch based ARS service when an AIN based service is provided.
FIG. 1 illustrates the known technique 1 of providing switch based ARS functionality using a DMS-100 switch when an AIN service is provided. As illustrated the method begins in step 3, e.g., with the start of a call being processed by an SSP which is a DMS-100. In step 5, the call activates an AIN trigger at the DMS-100. Then, in step 7, the DMS-100 halts processing of the call and then, in step 9, transmits a call processing message to an SCP. In step 11, the SCP accesses a CPR based on information received in the call processing message received from the DMS-100 and determines how the call should be processed, e.g., in accordance with an AIN service being provided. After determining how the call should be processed, the SCP, in step 13, generates a response message which includes a route index corresponding to the DMS-100's ARS table. Then, in step 15, the SCP transmits the generated message including the route index corresponding to the DMS-100's ARS table to the DMS-100 SSP. In response to the message and the route index included therein which corresponds to the switch's ARS table, in step 17, the DMS-100 accesses its switch based ARS table and uses it to determine the actual route index to be used to route the call. Then, in step 19 the DMS-100 routes the call using the route index obtained from its ARS table. With the call routed, processing of the call stops in step 21. Where a route index corresponding to an actual trunk is received by the DMS-100 in a message from the SCP, the DMS-100 routes the call using the indicated trunk as opposed to determining the trunk to be used from its ARS table.
The known technique illustrated in FIG. 1 relies on the SCP returning to a DMS-100 switch a route index which corresponds to the switch's ARS table as opposed to an actual trunk coupled to the DMS-100. Since the returned route index is a number corresponding to the DMS-100 ARS table there is no need to maintain an ARS table outside the switch, i.e., route indexes corresponding to actual trunk lines coupled to the switch need not, and are not, stored in the SCP as part of the known DMS-100 method of providing ARS in conjunction with AIN services. Unfortunately, telephone switches from other equipment providers do not include the ability to process a route index corresponding to an ARS table in the manner that the DMS-100 does. Accordingly, while this DMS-100 feature can be used to provide switch based ARS functionality to AIN service subscribers, telephone service customers who are serviced by switches from other manufactures can not take advantage of this functionality.
In order to avoid becoming overly dependent on a single equipment provider, most telephone companies purchase telephone switches from multiple vendors. As a result, a switch based feature available from a single vendor is generally not available to all customers of a telephone service provider since some customers will normally be serviced by a switch from a different vendor. From an implementation and customer satisfaction standpoint it is often desirable to deploy services in a manner that allows the services to be provided to customers regardless of which of the service provider's switches is used to service a customer. In some cases however, because of cost or other advantages, service providers are willing to allow different services to be offered to different customers.
In view of the above discussion, it becomes apparent that there is a need for new and improved methods of providing ARS services in conjunction with AIN services. Given that telephone service subscribers may be serviced by different telephone switches, e.g., some of which do not include the ARS functionality of the DMS-100 switch, it is desirable that at least some methods of providing ARS service be independent of the above discussed DMS-100 functionality. From an implementation standpoint, it is desirable that at least some new methods of providing ARS in conjunction with AIN service be capable of being implemented without requiring the deployment of new telephone switch hardware.
While table based ARS switch functionality has proved beneficial to a wide range of users, as the complexity of telephone systems and service provider relationships increases, it would be nice if ARS service could be enhanced to include conditional logic as part of the route selection process as an alternative to, or in addition to, the current route index look-up capability made possible by existing switch based routing tables.